As evidenced by U.S. Pat. Nos. 3,287,452, 3,398,149, 3,427,315, 3,671,649, 4,059,582, and 4,092,314 and Japanese Patent Publication Nos. 42-7915 and 51-26897, there are several known methods of preparing adenine. A particularly attractive method--a simple, one-step process for preparing adenine by reacting hydrogen cyanide with formamide in the presence of an ammonium salt and a catalytic amount of methyldisulfide at elevated temperatures--is taught in application Ser. No. 331,036 (Shin), filed Dec. 16, 1981, now U.S. Pat. No. 4,391,977. This process generally provides adenine in good yields but has the disadvantage of leading to the formation of a black polymer by-product which may constitute about 7-62% of the total product. The polymer formation, which results from the exothermic nature of the reaction, decreases adenine yields and leads to filtration difficulties, material losses on the filter and in solids handling, and increased operating and equipment costs.